Heavy metal pollution in the Quaternary Garza basin: A multidisciplinary study of the environmental risks posed by mining (Linares, southern Spain)

- Geophysical prospecting was applied for morphological analysis of tailings dams.
- High concentrations of metals were detected in slimes and surrounding soils.
- The surface and groundwater quality was affected by soil contamination.

In the metallogenic district of Linares (Jaén, Spain), intense deep mining associated with vein-type deposits of Pb and Cu has been conducted for centuries and has generated large mine waste accumulations. The objective of this study was to elucidate the influence of these mine wastes on the quality of the soil, the surface water and the groundwater. For this purpose, a sedimentary endorheic basin in the mining district was selected as the study location: the Quaternary Garza basin.The characterisation of the basin geometry and the tailings dams in the area was conducted by electrical resistivity imaging (ERI), which was supported with data provided by mechanical probing. The ERI data indicated that the basin is bounded by fractures that cause sudden changes in the thickness of the sedimentary cover and the wedging of the layers toward the edges of the basin. Furthermore, the resistivity profiles allowed the morphological identification of the deposits associated with the tailings dams. In addition, zones of weakness, preferential groundwater flow paths and the contact between the slimes deposits and the substratum were identified. These results confirmed the absence of impervious barriers at the tailings sites, which is a situation that poses a high pollution risk for soils and waters.A geochemical characterisation of the tailings dams and the surrounding soils indicated the presence of a high concentration of metals and metalloids. Of the 19 elements analysed at the dams, it is important to highlight the following values expressed in mg kg− 1: 19 913 for Pb, 418 for Cu, 4149 for Mn, 43 for As, 190 for Zn and 26 200 for Fe.Furthermore, the hydrochemical data showed the mobilisation through the aqueous media of certain heavy elements (Fe, Mn and Pb) that originate from lixiviation at these ancient tailings impoundments and from the adits that drain mine waters.